This research is a survey research. Its purposes were 1) to study the factors that caused the accidents of flight operations in the Royal Thai Army Aviation Units 2) to study and assess the risks of accidents in the Royal Thai Army Aviation Units and 3) to provide guidelines for commanders, pilots and personnel related to aviation to reduce the risk factors affecting the flight operations of the Royal Thai Army Aviation Units. The population in this research were 300 pilots of the Royal Thai Army Aviation Units. Questionnaires were used as research tool. The statistics used were frequency, percentage, mean, standard deviation, t-Test and one way ANOVA by using statistical package program. The results revealed each aspect as follows: 1) personal factors in terms of marital status: there was the possibility to risk factors in the areas of man, machine, media and mission. In terms of education level: there was the possibility to risk factors in the areas of machine, media, mission and management. 2) Factor of flight experience in terms of flight hours of current specific aircraft: there was the possibility to risk factors in the areas of man and media. In terms of monthly average number of flight operations: there was the possibility to risk factors in the areas of media, mission and management. 3) Factor of aviation knowledge, topics in education and training in aviation. Those who never study in Aviation Safety Officer Course: there was the possibility to risk factors in the areas of overall, machine and management. The results of the risk assessment found that 1) the man factor was a moderate risk 2) the machine factor was a moderate risk 3) the media factor was a high risk 4) the mission factor was a moderate risk and 5) the management factor was a high risk. Guidelines for reducing risk factors of the research results, proposed to the commanders to consider issuing the regulations to reduce the risk factors affecting the flight operations of the Royal Thai Army Aviation Units.